1. Field of the Invention
This invention is directed to a process for the waste treatment of solutions containing dissolved metals, espescially metal plating solutions, utilizing a metal recovery module containing a filler of catalyzed foam.
2. Description of the Prior Art
Solutions capable of plating metal are well known in the art. The most commonly used metal plating solutions comprise electrolytic and electroless solutions, the latter being capable of plating metal without the need for electricity.
The most frequently used electroless solutions for plating metal comprise copper and nickel plating solutions. Such solutions generally comprise four major ingredients dissolved in water. These ingredients include (1) a source of the metal plating ions, (2) one or more complexing agents capable of maintaining said metal ions in solution, (3) a reducing agent capable of reducing said metal ions to metallic form in the presence of a catalytic surface and (4) a pH adjustor to maintain solution pH within a desired range.
Electroplating solutions are used to plate a variety of metals and bear some resemblance to electroless plating solutions. However, they typically do not require reducing agents for plating and many do not require complexing agents.
The major ingredients of plating solutions are well known. Representative electroless nickel and copper plating solutions are disclosed in U.S. Pat. Nos. 3,329,512; 3,383,224; 3,650,777; 3,674,516; 3,915,715; and 4,036,651, all of which disclose the compositions of known plating solutions. The contents of these patents are incorporated herein by reference. Representative electrolytic metal plating solutions are disclosed in the Metal Finishing Guidebook and Directory, Metals and Plastics Publications, Inc., Hackensack. N.J. 1976, pp. 177 to 338. The contents of this portion of the handbook are also incorporated herein by reference.
It is known in the art than when electroless metal plating solutions are used, the content of various components of the solution are consumed. For example, as plating proceeds from an electroless plating solution, the concentration of both the metal and reducing agent are decreased. It is also known that metal plating solutions can be replenished by addition or replenishment of consumed ingredients to prolong the useful life of the solution. Thus, it is conventional to add a replenisher formulation consisting primarily of an aqueous solution of the metal salt and reducing agent. This results in an increase in the volume of the plating solution. Often, the excess solution must be waste treated.
Though the useful life of a plating solution may be prolonged by replenishment, eventually the solution becomes unsatisfactory and disposal is necessary. Consequently, the spent solution must be waste treated.
Another by-product of the plating operation is the rinse waters used to wash parts as they pass from one treatment solution to another. These rinse waters collect dissolved metal and other contaminants and often, these rinse waters must be waste treated. Consequently, there are numerous solutions resulting from the metal plating operation that must be waste treated including growth from the plating solution, spent solutions and rinse waters. Accordingly, for purposes of definition, the term plating solution as used herein is defined broadly to include solutions containing dissolved metals and in the case of electroless metal plating solutions, active complexing agent whether derived from the plating solution, rinse waters or growth or any combination of solutions resulting from a plating line.
The composition of several typical metal plating solutions, at initial make-up and when spent, are set forth below for purposes of illustration. The concentrations of the components of the spent solution are given as a range because they can vary within very broad limits dependent upon the source of the solution as discussed above. Hence, the ranges given should be viewed as illustrative only and should not be interpreted as limitations to the scope of the invention.